Effect of Al addition to the multi-principal elemental Al_xCrFeNiCu alloy system in terms of the resulting microstructure and ion irradiation response

Recently, high-entropy alloys (HEAs) and multi-principal elemental alloys (MPEAs) have attracted attention as potential new structural materials for in-core nuclear reactor applications, thanks to their structural stability and excellent mechanical properties. However, their multi-phase microstructural behavior under irradiation requires further attention, as it is crucial for understanding the irradiation behavior of the alloys. The current work compares the radiation behaviors of the Al_0.3CrFeCuNi (0.3Al) and Al_0.8CrFeCuNi (0.8Al) alloys, which were prepared via spark plasma sintering and then irradiated in situ in a transmission electron microscope (TEM) using 1-MeV Kr⁺ ions and up to 10 displacements per atom (dpa) at room temperature (RT) and at 300°C. Pre-irradiation characterization of the alloys was performed using x-ray diffraction (XRD) and transmission electron microscopy, revealing the formation of major proportions of (face-centered cubic [FCC] + body-centered cubic [BCC]) phases. A higher Al content spurred transformation from the FCC phase to the BCC phase and sparked the formation of ordered phases. While the alloy containing 0.3Al (FCC) exhibited irradiation-induced ordering at both RT and at 300°C, the 0.8Al alloy showed irradiation-induced disordering of the ordered phases at 300°C. The pre- and post-irradiation transmission electron microscopy experiments evidenced how variations in local chemistry and microstructural features in these MPEAs affect the local response to irradiation (at the nm/µm level). This study provides an overview of how structurally and chemically different phases in MPEAs react when under irradiation, affording crucial knowledge for understanding the irradiation resistance of the alloys.